Various gravity feed liquid supply assemblies have been used for supplying liquids to be sprayed to liquid (e.g., paint) spraying devices such as spray guns, including the liquid supply assembly including a collapsible liner that is described in International Publication Number WO 98/32539 (Joseph) of Jul. 30, 1998, the content whereof is incorporated herein by reference. That liquid supply assembly described in WO 98/32539 includes a container of stiff polymeric material comprising a generally cylindrical side wall and a bottom wall at a bottom end of the side wall with an opposite top end of the side wall defining an opening into a cavity in the container, and a flexible liner within that cavity. That liner corresponds in shape to an inner surface of the container, and has an annular lip along the top end of the side wall that defines an opening into a cavity in the liner. That liquid supply assembly further includes an adapter assembly comprising a central portion having a through opening that is adapted to engage the inlet port of the gravity fed liquid spraying device, a transverse portion including a peripheral part adapted for engagement within the flexible liner adjacent the top end of the container, and means for releasably securing the flexible liner around that peripheral part of the adapter assembly. The flexible liner within the cavity in the container can be used as a receptacle for measuring and/or mixing liquids to be sprayed, and markings or indicia are provided along the side of the container that enable the volume of the contents of the container to be determined, and can facilitate measuring liquid components. After the liquid is in the liner the adapter assembly is engaged with and secured to the flexible liner adjacent the top end of the container, and is engaged with the inlet port of a spraying device or spray gun. When the spray gun is operated with the container above the spray gun, both pressure from the fluid column in the container and suction from a venturi in the spray gun will cause liquid from the liner to enter the spray gun, whereupon the liner will collapse and decrease in volume to just contain the amount of liquid remaining in the liner. When the spray gun is positioned with the container below the spray gun (as can be desirable, for example to spray the underside of a structure), the fluid column in the liner can cause a negative pressure at the inlet to the spray gun. Most spray guns produce enough suction to overcome that negative pressure and withdraw sufficient liquid from the liner in a filled container that has a capacity of about 20 ounces or 600 milliliter to provide a useful spray pattern. When the filled container has a capacity of a significantly larger size such as about 32 ounces or 950 milliliters, however, the negative pressure at the inlet of the spray gun when the spray gun is operated with the container below the spray gun will can have a noticeable negative effect on the spray pattern produced by the spraying device compared to the spray pattern produced when the container is positioned above the spray gun.
Other types of gravity feed liquid supply assemblies that have been used for supplying mixtures of component liquids to be sprayed to liquid (e.g., paint) spraying devices or spray guns include the type of liquid supply assembly used on the “SATA” (t.m.) NR-95,NR-92, or Jet B Spray guns commercially available from Sata, Farbspritzechnik GmbH & Co., Kornwestheim, Germany, modified to include a HVLP (i.e., high volume, low pressure) Pro Upgrade Kit available from Lex-Aire Products, Inc., North Billerica, Mass.; the type of liquid supply assembly used on the “LEX-AIRE” (t.m.) 2002 HVLP spray gun commercially available from Lex-aire Products, Inc., North Billerica, Mass.; and the type of liquid supply assembly used on the “GRACO” (t.m.) Turbine HVLP 4900 Fine Finish Sprayer commercially available from Graco, Inc., Minneapolis, Minn. Those liquid supply assemblies include a container of stiff polymeric material comprising a generally cylindrical side wall and a generally conical bottom wall at a bottom end of the side wall with an opposite top end of the side wall defining an opening into a cavity in the container. An adapter connects a through opening in the bottom wall to an inlet port of the gravity fed liquid spraying device. Liquids to be sprayed are poured into the cavity, and a liquid and air tight cap is attached to the top end of the side wall. As the liquids are sprayed low pressure air (e.g., in the range of about 0.5 to 8 pounds per square inch or 3.5 to 55 kilopascals) is supplied to the cavity through an air supply line having one end extending through the cap, and its opposite end engaged with a supply of that low pressure air developed in the spray gun (e.g., from the supply of air used to shape the spray stream) when the spray gun is being operated to spray the liquid from the container. This low pressure in the cavity of the container is said to provide certain advantages including finer atomization and a faster —14 inch (35.6 cm) wide fan pattern. Liquid supply assemblies of this type, however, can only be used with the top end of the container generally uppermost, for if the container is tipped very far from that position, the liquid column that feeds liquid into the spray gun can be lost, and liquid can enter the air supply line causing it to plug, and/or liquid to flow through it into parts of the spray gun where it will cause operational or cleaning problems.